1. Field of the Invention
This invention relates to fabric-softening products suitable for use at elevated temperatures encountered in laundry dryers. In particular the invention relates to impregnating liquid fabric softening agents into absorbent substrates.
2. Description of the Prior Art
Surface modification of fabrics, particularly cellulosic fabrics, to soften and impart properties such as antistatic, lubricating, bacteriostatic, mildew-proof and moth-proof properties has been accomplished by treating the fabrics with appropriate chemicals for modifying such properties. It is now common practice to treat various types of household apparel and fabrics with one or more specialized conditioning agents which affect the softness of the fabrics.
For various beneficial reasons, the practice has recently developed of softening and otherwise conditioning household apparel and fabrics during drying after laundering. Fabric conditioning products comprising sheet goods (substrate) coated or impregnated with a fabric-softening chemical and/or other specialized fabric conditioning chemicals have been commingled with damp laundry during the drying of the laundry at the elevated temperatures encountered in a typical household laundry dryer. At the elevated temperature, specialized fabric conditioning chemicals are released from the product and transferred to the commingled fabrics during drying.
Typical absorbent sheet goods employed as a substrate for heat-activated, fabric-softening products include flexible foam, felted, non-woven, and wet-lay fibrous sheets such as paper toweling, scrims, cloth, and air-lay webs containing cellulosic or synthetic fibers of papermaking-length or longer. For example see U.S. Pat. No. 3,442,692 entitled METHOD OF CONDITIONING FABRICS.
Fabric-softening chemicals and other specialized chemicals for conditioning fabrics have been coated onto thin substrates. Preferably, to avoid staining and other problems during drying, the conditioning chemicals have been impregnated into absorbent substrate in combination with controlling the absorbent characteristics of the substrate. For example see U.S. Pat. No. 3,686,025 entitled TEXTILE SOFTENING AGENTS IMPREGNATED INTO ABSORBENT MATERIALS.
Fabric conditioner chemicals have been applied in liquid form (a molten bath or a solution made with a solvent) to the absorbent substrate and then solidified (by cooling or evaporating the solvent).
Impregnating absorbent substrates with liquid fabric conditioning agents was previously accomplished by applying excess liquid to the substrate followed by squeezing off excess liquid with rollers forming a compression nip. A typical disclosure of the technique of applying excess liquid to the absorbent substrate followed by squeezing off the excess with rollers is contained in U.S. Pat. No. 3,686,025 from column 14, line 68 to column 15, line 44.
British Patent No. 1,419,647 discloses another method of impregnating an absorbent substrate with one roller. Substantial compression of the substrate is avoided (see page 5, lines 30 to 35).
Applying a discrete surface coating to a paper type web is disclosed in U.S. Pat. No. 3,895,128. However, impregnating a web is not taught (see column 7, line 47 to column 8, line 23).